Laser induced fluorescence imaging: application to groups of macroalgae identification

Up to now, no technique was available to perform inventories and surveys of immersed macroalgae. This article presents a method making it possible to discriminate between macroalgae and seafloor and to identify the various macroalgae. groups (green, brown or red). To our knowledge, this is the first excitation-emission matrix (EEM) of macroalgae ever carried out allowing the identification of the spectral characteristics of each macroalgae group. Fluorescence imaging provides the spatial dimension besides spectral properties. An optical parametric oscillator (OPO) laser excites a test scene of macroalgae in a seawater aquarium. Laser-induced fluorescence images from 400 to 640 nm displayed by steps of 10 nm are filtered at 680 nm. Their analysis, combined with the water depth parameter, leads to an identification method for macroalgae. groups in a false-colour image: each of the three macroalgae. groups is enhanced by one defined threshold on this false-colour image.